This invention relates to conveyor belts for carrying bulk material and in particular conveyor belts which are supported on conventional troughing rolls. Such belts are required to be strong and almost inextensible in the longitudinal direction and to have a moderate stiffness transversely, so that the longitudinal driving loads will be sustained and the belts will bend into the desired trough shape while bridging the angles between the several troughing rolls in each group.
A great many combinations of reinforcing materials have been proposed to impart the desired properties to conveyor belts of rubber or other elastomers for carrying bulk materials, but the majority of such belts continue to be reinforced with multiple plies of woven fabrics, or a multi-ply woven fabric having a plurality of layers of longitudinal yarns, or, alternatively, uniformly spaced longitudinal cords or cables combined with a transverse stiffener. Such belts, when carefully made, track satisfactorily over the head and tail pulleys and the intervening idler rolls, but require closely spaced expensive troughing rolls to provide adequate support and to prevent spillage. One of the main factors leading to spillage seems to be the flattening of the belt between idlers brought about by the high tension required to drive such belts and the inherent flexibility of woven fabrics, cords or cables embedded within the rubber or elastomer forming the body of the belt.
Attempts have been made to control spillage by adding upstanding rubber flanges to the edges of belts which are otherwise of conventional construction, but such flanges not only do not prevent transverse flattening between successive troughing idlers, but present other problems such as difficulties in passing around end pulleys, particularly if the flanges are high enough to be of significant benefit in preventing spillage.
In addition, proposals have been made to provide supports for conveyor belts omitting longitudinal reinforcements over a part or all of their width. Thus, so-called “cable belts,” made without longitudinal tension members, ride on a pair of moving steel cables, which permits elimination of inclined troughing rolls but requires addition of separate sheaves for guiding and transmitting power to the cables. Other proposals are to omit some of the longitudinal reinforcement at a particular zone, such as an edge or the center of the belt, but the remaining reinforcement in such cases is of a conventional kind and located in a conventional relation to the transverse reinforcement.
Belts having metal cores or carcasses have been proposed in the past. However, such belts do not provide the desired longitudinal and lateral strength and flexibility of the present invention.
For example, one of the earliest examples, Emery, U.S. Pat. No. 420,779, provides two layers of an ordinary leather belt with parallel metal strips arranged in the longitudinal direction and cemented between the layers. No lateral connection between the strips is evident.
Similarly Harley, U.S. Pat. No. 757,919, provides a longitudinal metal band between two layers of belt material with the edges of the belt material stitched to enclose the band. When a wide belt is constructed, a plurality of bands are provided and the belt material stitched between the bands. As with Emery, there is no lateral connection providing no lateral stiffness to the belt.
Pattee, U.S. Pat. No. 1,204,816, discloses a belt which is constructed of a plurality of interwound spiral coils disposed parallel to each other in a lateral arrangement across the belt. The coils are secured to endless flexible cables disposed along the longitudinal edges of the belt. When the belt body is made of rubber it fills the interstices of the coils embedding them within the rubber body.
Shiner, U.S. Pat. No. 1,360,456, discloses a reinforced belt where the reinforcing element is a link chain of the type consisting of U-shaped links with the arms of each link being apertured to receive the bend of the adjacent link. The chains are embedded within the belt material in parallel rows along the longitudinal axis of the belt.
Paul, U.S. Pat. No. 1,527,912, discloses a belt core consisting of a strip of metal provided with a plurality of pairs of slits with the metal between the slits being pressed outwardly in opposite directions to form transversely extending circular openings.